The present invention relates to damper mechanisms and, more particularly, to bearing assemblies for use in damper mechanisms. The invention has particular application to damper mechanisms used furnaces such as those used in vapor generation apparatus,
The present invention may be used in dampers for controlling supplemental air flow into the fuel-air admission assemblies of such furnaces. It is a design requirement that the assembly of the present invention seal off the hot internal furnace gases and prevent them from passing to the outside of the furnace. A prior art design uses three separate concentric tubular members. The largest tubular member is a bearing housing that is fixed to the duct. The next largest tubular member is a sleeve or journal bearing that rotates in the bearing housing. The smallest tubular member is a gland nut that secures packing against the shaft on which the damper blade turns.
The packing seals off the internal gases and coal dust with a seal assembly like that used in the common stem faucet used in residential bathrooms. More particularly, a preformed packing, shaped something like a rope, is wrapped around the damper shaft and a packing or gland nut engages the bearing housing to compress the packing. A disadvantage of this procedure that it is difficult to adjust the gland nut to provide adequate sealing without increasing rotational fiction loading of the damper shaft.
Each of the parts of the prior art seal and bearing assembly must have very precise concentricity requirements. If the surfaces on the respective members are not precisely aligned ,a binding force is put on the shaft.
In the prior art design a damper shaft operating lever is attached to the shaft by drilling a hole through the shaft and a lever to permit insertion of a pin. If the lever is not properly located, the damper may not work properly. The relative position of the shaft and the lever is of vital significance for proper operation of the damper. Misalignments of even one-half of one degree may be a problem for some applications. For example, leakage through the damper may occur that will be objectionable.